Chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrochlorocarbons (HCCs, e.g., 1,1,1-trichloroethane and carbon tetrachloride) have been used in a wide variety of solvent applications such as drying, cleaning (e.g., the removal of flux residues from printed circuit boards), and vapor degreasing. These materials have also been used in refrigeration and heat-transfer processes. However, the photolytic and homolytic reactivity at the chlorine-containing carbon sites has been shown to contribute to depletion of the earth's ozone layer. Additionally, the long atmospheric lifetime of CFCs has been linked to global warming. As a result, there has been a world-wide movement for over a decade to replace CFCs. (See “Montreal Protocol on Substances That Deplete the Ozone Layer,” Copenhagen Amendments, United Nations Environment Program, 1992).
The characteristics sought in replacements, in addition to low ozone depletion potential, typically have included boiling point ranges suitable for a variety of solvent cleaning applications, low flammability, and low toxicity. For some applications, solvent replacements should also have the ability to dissolve both hydrocarbon-based and fluorocarbon-based soils. In some embodiments, solvent replacements also have low toxicity, have no flash points (as measured by ASTM D3278-98 e-1, “Flash Point of Liquids by Small Scale Closed-Cup Apparatus” otherwise known as SETAFLASH), have acceptable stability, have short atmospheric lifetimes, and have low global warming potentials.
Hydrofluoroethers (HFEs) have gained interest as replacements for CFCs and HCFCs. Generally, HFEs are chemically stable, have low toxicity, are non-flammable, and are non-ozone depleting. Mixtures of HFEs with other organic solvents tend to be better solvents and dispersants for hydrocarbons than HFEs alone.
Many azeotropes possess properties that make them useful solvents. For example, azeotropes have a constant boiling point that avoids boiling temperature drift during processing and use. In addition, when an azeotrope is used as a solvent, the properties of the solvent remain constant because the composition of the solvent does not change during boiling or reflux. Azeotropes that are used as solvents also can be recovered conveniently by distillation.
In some embodiments, it is desirable to provide azeotropes or azeotrope-like compositions that have good solvent strength. In another aspect, in some embodiments, it is desirable to provide azeotropes or azeotrope-like compositions that have low flammability. In yet another aspect, in some embodiments, it is desirable to provide azeotropes or azeotrope-like compositions that are non-ozone depleting, and/or have a relatively short atmospheric lifetime so that they do not significantly contribute to global warming (i.e., azeotropes or azeotrope-like compositions that have low global warming potential).